PubMed Health⌕ Search

Biomedical subjects

J F Souhrada

Publications and source records attributed to J F Souhrada.

At least 19 recordsLinked to original sources
PubMed1991

Respiratory epithelium-dependent inhibition of protein kinase C of airway smooth muscle cells.

We have examined the effect of phorbol myristate acetate (PMA) on airway smooth muscle (ASM) in the presence and absence of respiratory epithelium (RE) and analyzed the dependence of this response on extracellular sodium, Na+/H+ exchange, calcium, and cyclooxygenase products; we determined both the resting membrane potential and isometric force developed by ASM preparations. Removal of RE had no effect on the values of the resting membrane potential of ASM cells. In the presence of RE in the preparation, both electrical and contractile responses to PMA (10(-5) M) were significantly different compared with the response of ASM to PMA without RE. When the RE was present, stimulation of protein kinase C caused only a biphasic response in both membrane potential and isometric force. In either the presence or absence of RE, amiloride (10(-5) M) and a low-sodium solution inhibited both electrical and contractile changes of ASM cells caused by PMA. In the presence or absence of RE, verapamil (10(-5) M) attenuated (P less than 0.05) both electrical and contractile responses of ASM cells as induced by PMA. Verapamil, however, had no effect on the last phase of PMA-induced response. Pretreatment of preparations with indomethacin (10(-6) M) changed the PMA-induced response of ASM with RE to a response usually observed in ASM without RE. Finally, the incubation of tracheal preparations without RE with prostaglandin E2 (10(-8) M) altered the response of these preparations in such a way that their electrical and contractile response to PMA was essentially identical to the PMA response observed in preparations with an intact RE.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1989

Sodium and calcium influx induced by phorbol esters in airway smooth muscle cells.

The second messenger protein kinase C (PKC) may play a critical role in the regulation of smooth muscle tone. In this study we examined how a direct stimulation of PKC in airway smooth muscle (ASM) cells influences the electrical and contractile properties of these cells. ASM preparations were obtained from adult male guinea pigs (Camm-Hartley strain). Changes in both the resting membrane potential (Em), as measured by a glass microelectrode technique, and the isometric force, measured by a copper-beryllium strain gauge, were continuously monitored. All experiments were done at the optimal length (Lmax) of ASM preparations and a temperature of 37.0 +/- 0.5 degrees C. The effects of phorbol myristate acetate (PMA), phorbol 12,13-diacetate (PDA), and 12,deoxyphorbol-13-isobutyrate (DPB) were investigated (with concentrations ranging from 10(-10) to 10(-4) M). We found that: (1) administration of all three phorbol esters caused a triphasic electrical and contractile response of ASM preparations showing initial, rapid depolarization, an increase in the isometric force, and slow hyperpolarization and relaxation of ASM followed by slow depolarization and an increase in the isometric force; (2) the presence of specific PKC inhibitor H-7 (10(-5) M) prevented development of both electrical and contractile events as induced by tested phorbols; (3) amiloride (10(-5) M) attenuated first- and second-phase responses, whereas furosemide (10(-5) M) inhibited all three responses (a sodium-free environment attenuated all three responses); (4) ouabain (10(-5) M) inhibited a second-phase response, whereas verapamil (10(-6) M) partially attenuated all three phases.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1989

The role of protein kinase-C in sensitization and antigen response of airway smooth muscle.

Recently, we reported the characteristic electrical and contractile changes of airway smooth muscle (ASM) preparations after administration of highly purified antiovalbumin immunoglobin G1 (IgG1). Because these changes are comparable to those we observed after administration of several phorbol esters, we theorized that sensitization of ASM with IgG1 leads to the activation of protein kinase-C. Therefore, in this study we examined the effect of two inhibitors of protein kinase-C on the sensitization-induced changes of ASM cells. ASM preparations were obtained from adult male guinea pigs (Camm-Hartley strain). Changes in both the resting membrane potential, as measured by a glass microelectrode technique, and changes in the isometric force, measured by a copper-beryllium strain gauge, were continuously monitored. Experiments were conducted at the optimal length of ASM preparations and a temperature of 37 degrees C. The preparations were pretreated with H-7 (1-(5-isoquinoilinyl-sulfonyl)-2-methyl piperazine) or NA-0345 (N,N-dimethylamino-methyl-SF2370) both protein kinase-C inhibitors, passively sensitized with IgG1 and consequently exposed to a specific antigen. We found that pretreatment inhibited the initial depolarization and the increase in the isometric force, usually observed after administration of IgG1, and that it attenuated ovalbumin-induced depolarization and sustained increase in the isometric force. These effects were concentration-dependent and were observed only when protein kinase-C inhibitors preceded administration of IgG1. Finally, H-7 pretreatment had no effect on KCl- or substance-P-induced physiologic changes but partially attenuated response to histamine.(ABSTRACT TRUNCATED AT 250 WORDS)

1-(5-Isoquinolinesulfonyl)-2-Methylpiperazine↗
PubMed1988

Doxazosin in patients with hypertension.

The antihypertensive effects and steady-state pharmacokinetics of doxazosin, as well as the bioequivalence of four dosage forms, were studied in 25 hypertensive patients. For an 8 mg daily dose mean Cmax at steady-state for all patients was 108 ng/ml; the mean tmax was 1.8 h. The mean terminal elimination half-life was 22 h. The four tablets containing 1, 2, 4, or 8 mg of doxazosin were bioequivalent in delivering the 8 mg dose. In patients with mild to moderate hypertension, 26-day treatment with doxazosin resulted in blood pressure reduction of 10/7 mmHg in the supine and 13/18 mmHg in the standing position. Adverse effects were generally mild and of brief duration.

Adult↗
PubMed1988

Corticosteroids attenuate sensitization-induced membrane changes in airway smooth muscle cells.

Serum from immunized guinea pigs or highly purified IgG1 induces specific changes in electrical and contractile characteristics of airway smooth muscle (ASM) cells. In this study, the effect of hydrocortisone and prednisolone pre-treatment on the events caused by a passive in vitro sensitization of ASM cells was investigated. ASM preparations isolated from male guinea pigs were exposed to immunized serum (1:10 dilution) together with different concentrations of hydrocortisone or prednisolone administered simultaneously or 30, 120 or 240 min before addition of immunized serum. During sensitization as well as during consecutive specific antigen challenges (1 mg/ml ovalbumin), both the resting membrane potential (Em) and isometric force developed by airway smooth muscle preparations were determined. Em was determined with glass microelectrodes and isometric force was simultaneously measured with a copper-berylium strain gauge. Pretreatment with both hydrocortisone and prednisolone (in the range of 10(-8)-10(-4) M) attenuated sensitization-induced transient depolarization and steady state hyperpolarization of ASM cells and decreased the sensitization-induced development of the isometric force. Furthermore, pretreatment with either steroid significantly attenuated electrical and contractile responses to a specific antigen challenge. Inhibition of the events observed during sensitization occurred at steroid concentrations as low as 10(-8) M. We have also found that the duration of exposure of ASM cells to either of the tested steroids is critical in determining the magnitude of this inhibitory effect and seems to be more important than concentration of tested steroids.(ABSTRACT TRUNCATED AT 250 WORDS)

Adrenal Cortex Hormones↗
PubMed1988

The inhibition of sodium influx attenuates airway response to a specific antigen challenge.

1. We have previously observed that manipulation of Na+ availability during passive in vitro sensitization altered electrophysiological and contractile changes of airway smooth muscle cells. The purpose of this study was to establish whether interference with Na+ influx during sensitization also influences the response of airway smooth muscle, both in vivo and in vitro, to a specific antigen challenge. 2. Isolated segments of trachea which had been sensitized to ovalbumin in the presence of the Na+ channel-blocking agent amiloride (10(-5) M) showed no electrical or contractile response to ovalbumin in spite of their ability to respond to histamine (10(-5) M). 3. Airway smooth muscle preparations sensitized to ovalbumin in a Na+-deficient medium failed to show any contractile response after exposure to ovalbumin and only a small depolarization of airway smooth muscle cells was detected. 4. Guinea-pigs were passively sensitized in vivo either in the absence of, or following pretreatment with, amiloride (1 mg kg-1 s.c.). These animals were then exposed to an ovalbumin inhalation challenge and both lung resistance (RL) and dynamic lung compliance (Cdyn) were measured. 5. After an inhalation challenge of sensitized animals, we observed a significant increase in lung resistance (RL) achieving a maximum of 489% of the baseline values and a decrease in dynamic lung compliance (Cdyn). Twenty min after ovalbumin challenge Cdyn was equivalent to 20% of baseline values. 6. In animals pretreated with amiloride during sensitization, the inhalation challenge caused only a small increase in RL achieving a maximum increase of 148% of baseline values, and a small decrease in Cdyn. Twenty min after ovalbumin challenge Cdy. was equivalent to 98% of baseline values. 7. We concluded that interference with Na' influx during both in vitro and in vivo sensitization attenuates the contractile and electrical responses of airway smooth muscle preparations or the changes in lung resistance and compliance observed after antigen challenge.

Amiloride↗
PubMed1988

Specific reaginic antibody IgG1-induced changes of airway smooth muscle cells.

It was found that 1) an administration of both immunoglobulin G1 (IgG1) or immunized serum caused an immediate depolarization and an increase in the isometric force of airway smooth muscle (ASM) cells, followed by a sustained hyperpolarization and a return of the tone to the base-line values; 2) an IgG1 concentration-dependent relationship was found between a peak depolarization, a peak hyperpolarization, and a peak isometric force; for these events 50% effective dose (ED50) was found to be 0.17, 0.14, and 0.25 microgram/ml of IgG1, respectively; 3) both electrical and contractile responses to ovalbumin of ASM cells sensitized with IgG1 were also dependent on the concentration of IgG1; the ED50 values of this relationship were 0.27 and 0.25 micrograms/ml of IgG1, respectively; 4) amiloride (10(-8) to 10(-5) M) pretreatment and a sodium-deficient environment attenuated sensitized-induced electrical and contractile changes as well as the response of ASM to ovalbumin (0.1%); and 5) pretreatment of ASM with diphenhydramine (10(-5) M) or FPL 55712 (10(-6) M) had no effect on sensitization-induced changes in membrane potential but attenuated electrical and contractile response of ASM to ovalbumin (0.1%).

Amiloride↗
PubMed1987

A transient calcium influx into airway smooth muscle cells induced by immunization.

We have recently reported that sensitization induced biphasic changes of resting membrane potential of the airway smooth muscle cells (Souhrada and Souhrada, 1985). To further clarify whether these changes may have any effect on the airway smooth muscle contractility, we have studied tracheal segments, isolated from Camm-Hartley guinea pigs during passive in vitro sensitization. At that time, airway smooth muscle cells were frequently penetrated with glass microelectrodes and the value of the resting membrane potential was determined simultaneously with changes in the isometric force. It was found that: changes in the resting membrane potential were accompanied by the alteration of the isometric force; during the depolarization phase a transient increase in the isometric force was observed achieving the maximal peak equal to 800 +/- 50 mg; both electrical and contractile changes of airway smooth muscle preparations as induced by sensitization were dependent on the dilution of sensitized serum; ED50 of this relationship was equal to dilution of 1:2500, while the maximal depolarization and the maximal peak isometric force developed at the dilution of serum 1:10; sensitization-induced sodium influx was critical for the development of the isometric force and depolarization, since pretreatment of tissues with amiloride (10(-5) M) or tetrodotoxin (10(-7) M) attenuated these changes; an increase in the isometric force was related to both the opening of the voltage dependent calcium channels and the release of calcium from the intracellular pools.

Airway Resistance↗
PubMed1987

Differential effects of N-formyl-methionyl-leucyl-phenylalanine and substance P on the electrical and contractile properties of airway smooth muscle cells.

We have investigated the effect of substance P (SP) and N-formyl-methionyl-leucyl-phenylanine (f-Met-Leu-Phe) on airway smooth muscle preparations isolated from male guinea pigs. Alterations in both the resting membrane potential and developed isometric force were determined. Addition of SP (10(-10) to 10(-4) M) caused a nonphasic, dose-dependent, sustained depolarization of airway smooth muscle cells, with the concomitant development of increased isometric force. In contrast, f-Met-Leu-Phe (10(-12) to 10(-6) M) induced a biphasic membrane response of airway smooth muscle cells, i.e., a dose-dependent rapid depolarization, followed by prolonged hyperpolarization. During the depolarization phase, a significant transient increase in the isometric force was observed. A selective N-formyl peptide antagonist, t-boc-phenylalanyl-leucyl-phenylalanyl-leucyl-phenylalanine, prevented the f-Met-Leu-Phe-induced changes in membrane polarity and increase in isometric force, as did amiloride (10(-5) M), the selective sodium channel blocker. However, these agents had no effect on SP-induced changes in membrane potential or isometric force. These findings suggest that airway smooth muscle of guinea pigs possess both N-formyl peptide and SP receptors but that occupation of these receptors by their respective agonists leads to functionally distinct responses.

Animals↗
PubMed1985

Sensitization-induced sodium influx in airway smooth muscle cells of guinea pigs.

Airway smooth muscle (ASM) preparations isolated from Camm-Hartley male guinea pigs were passively in vitro sensitized using Austen's technique. During this sensitization, cells were frequently penetrated with glass microelectrodes (a resistance of 80-90 M omega) for a period of 120 min. Simultaneously, changes in the isometric force of ASM preparations were also monitored. It was found that: administration of serum (1:10 dilution) from sensitized animals caused a depolarization of ASM cells (-52.3 +/- 0.7 mV), achieving a peak at 4 min, followed by slow sustained hyperpolarization reaching a steady state after 15 min; (Resulting resting membrane potential of ASM cells was -68.8 +/- 0.5mV as compared to membrane potential of controls equal to -60.0 +/- 0.7 mV); in the presence of ouabain (10(-5)M), the development of hyperpolarization of ASM cells was completely inhibited; replacement of Na+ with choline chloride or lithium chloride partially inhibited the development of depolarization of ASM cells; in the presence of specific sodium entry blocker, amiloride the sensitization-caused depolarization was abolished; the presence of choline chloride, lithium chloride or amiloride in the experimental medium completely inhibited the contractile response of sensitized tissues to a specific antigen; response of ASM preparations to a specific antigen was absent during depolarization of ASM cells, but was always present during their hyperpolarization. It is concluded that in vitro passive sensitization leads to the interaction of serum specific antibodies with the membrane of airway smooth muscle cells so that permeability of membrane for Na+ is increased (transient depolarization) followed by the activation of electrogenic Na+-pump (sustained hyperpolarization). These events seem to determine the contractile response of sensitized ASM cells to a specific antigen.

Amiloride↗
PubMed1985

Role of electrogenic Na+ pump in the response of sensitized airway smooth muscle to antigen.

Airway smooth muscle (ASM) preparations (mid-cervical portion of trachea) were isolated from control Camm-Hartley male guinea pigs and from animals repeatedly sensitized by ovalbumin. Simultaneously with the measurement of isometric force developed by ASM preparations, resting membrane potential (Em) was determined by employing a conventional microelectrode technique. The contractile and electrophysiological responses of normal and sensitized tissues to ovalbumin and histamine (10(-5) M) were measured during inhibition or stimulation of the electrogenic Na+ pump. The activity of the electrogenic Na+ pump was decreased by the temperature of the experimental bath, i.e., 21 +/- 0.5 degrees C, or by ouabain (10(-5) M). We found that: at 37 degrees C Em of ASM in controls was -60.3 +/- 0.4 mV (+/- SE) as compared to -78.2 +/- 0.4 mV (+/- SE) of ASM from resensitized animals (p less than 0.001); cooling (21 degrees C) decreased (p greater than 0.001) Em of ASM of both controls and resensitized animals; warming (40 degrees C) further increased (p less than 0.01) Em of control ASM but had no effect on Em of ASM from resensitized animals; when the electrogenic Na+ pump was inhibited by low temperature (21 degrees C) or by ouabain (10-5 M), ASM preparations from resensitized animals had no measurable response to ovalbumin; in ASM preparations from controls cooling (21 degrees C) potentiated (p less than 0.01) and warming (40 degrees C) attenuated (p less than 0.01) the histamine (10(-5) M) contractile response; in ASM preparations from resensitized animals, when the electrogenic Na+ pump was inhibited, significant (p less than 0.01) contractile and electrical responses to histamine (10(-5) M) were still present.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1979

Role of glucose in contractility of airway smooth muscle.

This study investigated the response of isolated tracheal preparation (ITP) from guinea pigs to three bronchoconstrictive drugs: histamine (H), carbachol (CAR), and acetylcholine (ACH). Cumulative dose-response curves were obtained in substrate-rich (5.50 mM of glucose) and substrate-free physiological salt solutions under aerobic conditions (PO2 = 95 +/- 0.5 Torr) or in acute 30-min hypoxia (PO2 = 30 +/- 2 Torr). The reactivity of ITP was measured by ED50 (effective dose developing 50% of maximal response); and the contractility of ITP was measured by a maximal developed isometric tension. This study showed that the contractile response of isolated segments of tracheas to H, CAR, and ACH was significantly decreased (P less than 0.05) when the experimental medium contained no glucose, or when glucose was replaced with metabolic inhibitor 2-deoxyglucose. This data contrasted with findings obtained with main pulmonary arteries (MPAs) isolated from the same species, where the absence of glucose in the experimental medium did not affect patterns of histamine cumulative dose-response curves. It was also shown that pretreatment of isolated tracheas with a small dose of insulin significantly decreased (P less than 0.05) the contractile response of airway smooth muscle to histamine. In both experiments, either with or without glucose in the experimental medium, acute hypoxia (30 min) had a significantly greater effect (P less than 0.05) on the development of isometric tension of MPA compared with that on ITP. Both removal of glucose from the experimental medium and/or acute hypoxia significantly decreased (P less than 0.001) adenosin triphosphate and creatine phosphate contents of tracheal segments but did not influence the high-energy phosphate content of main pulmonary arteries exposed to similar conditions. In addition to pointing out the physiological and metabolic differences between pulmonary vascular and airway smooth muscle, this study showed the important dependence of airway smooth muscle on glucose as a substrate.

Acetylcholine↗
PubMed1979

Postnatal changes in response of canine neonatal pulmonary arteries to histamine.

Postnatal development of histamine receptors in the canine pulmonary circulation was examined utilizing histamine cumulative dose-response curves of pulmonary arteries isolated from neonatal and adult dogs. The maximal contractile response to histamine was relatively low at birth (avg 0.069 g) and increased with postnatal age, reaching a maximum in the adult (avg 1.10 g). H2-receptor blockade with metiamide increased the contractile response to histamine during the first 2 wk of life (avg 0.38 g), suggesting H2-receptor dominance over H1-receptors in the newborn. Maximal developed tension, in response to KCl, gradually increased with postnatal age, suggesting progressive maturation of the smooth muscle response. In contrast to pulmonary arteries, isolated tracheal segments from puppies aged 1-5 days demonstrated large contractile responses (avg 5 g). Histamine (in microgram/g of wet wt of lung tissue) was absent in the lungs from 3rd trimester fetal dogs and rapidly increased over the first 2 wk of life, reaching a maximum in the adult. It is concluded that 1) the response of pulmonary arteries to histamine changes during the first 2 wk of life; 2) this change may reflect a decrease in H2-receptors and an increase in H1-receptors; 3) the contractile ability of pulmonary vascular smooth muscle increases with postnatal age; and 4) histamine is unavailable for physiological responses in the fetal dog pulmonary circulation.

Animals↗
PubMed1979

Airway response in asthmatic children during and after exercise.

This study investigated the effect of moderate treadmill exercise on the airways of normal and asthmatic children using an effort-independent method (total respiratory resistance) as well as conventional pulmonary functions. Changes in total respiratory resistance (Rrs) were measured during and after exercise using a forced oscillation technique. Conventional spirometric (PEFR, FEV1 and MMEF) and body plethysmographic measurements (Raw, Vtg) were also determined before and after exercise. A rapid, signigicant decrease in Rrs, suggesting bronchodilation during exercise, was observed in both groups tested, but this decrease was greater in normal children than in asthmatic patients. The bronchodilation persisted throughout the exercise period in both the asthmatic and the normal children. Increasing the length of the exercise from 10 to 20 min did not alter the degree or the duration of exercise-induced bronchodilation. In both normal children and patients with bronchial asthma, during moderate treadmill exercice, a significant, persistent bronchodilation can be detected. At the end of exercise, bronchoconstriction developed in asthmatic patients, while the values in normal subjects returned to their preexercise levels.

Asthma↗
PubMed1978

The beneficial effect of nasal breathing on exercise-induced bronchoconstriction.

In the first step of a study of the relation of nasal and oral breathing during moderate treadmill exercise to the onset of bronchoconstriction in young patients with perennial bronchial asthma, it was observed that most subjects spontaneously breathed with their mouths open when instructed to breathe "naturally." Subsequently, when they were required to breathe only through the nose during the exercise, an almost complete inhibition of the postexercise bronchoconstrictive airway response was demonstrated. When instructed to breathe only through the mouth during exercise, an increased bronchoconstrictive airway response occurred, as measured by spirometry, flow-volume relationships, and body plethysmography. These findings suggest that the nasopharynx and the oropharynx play important roles in the phenomenon of exercise-induced bronchoconstriction.

Adolescent↗
PubMed1978

The role of hyperventilation in exercise-induced bronchoconstriction.

Significant bronchoconstriction, comparable in severity to that observed after moderate treadmill exercise, was induced in asthmatic children by voluntary isocapnic hyperventilation of 3-min and 10-min duration. In both hyperventilation and exercise, nasal breathing inhibited the bronchoconstrictive responses, whereas mouth breathing potentiated the bronchoconstrictive response. In the asthmatic children, 10 min of voluntary isocapnic hyperventilation did not represent a greater bronchoconstrictive stimulus than did 10 min of exercise or 3 min of isocapnic hyperventilation. This study also showed that in normal children there was no measurable airway response after either voluntary isocapnic hyperventilation or moderate exercise. Finally, this study indicates that it is the stimulation of upper airway receptors by relatively cold and dry air, rather than hyperventilation per se, that provokes exercise-induced bronchoconstriction.

Adolescent↗